简述土壤重金属污染检测技术的进展及其在农业生态安全领域中的应用

本文旨在综述土壤重金属污染检测技术的最新进展,并探讨其在农业生态安全领域中的应用。首先介绍了土壤重金属污染的现状和危害。之后详细阐述了各种土壤重金属检测技术,包括传统的湿化学分析法、原子吸收光谱法、X射线荧光光谱法等,以及近年发展起来的生物传感器、纳米材料传感器等新型技术。然后讨论了这些技术在农业生态安全领域中的应用。最后,本文对未来土壤重金属污染检测技术的发展趋势进行了展望。

Advanced carbon materials for flexible and wearable sensors

Flexible and wearable sensors have drawn ex-tensive concern due to their wide potential applications inwearable electronics and intelligent robots. Flexible sensorswith high sensRivity, good flexibility, and excellent stabilityare highly desirable for monitoring human biomedical signals,movements and the environment. The active materials and thedevice structures are the keys to achieve high performance.Carbon nanomaterials, including carbon nanotubes （CNTs）,graphene, carbon black and carbon nanofibers, are one of themost commonly used active materials for the fabrication ofhigh-performance flexible sensors due to their superiorproperties. Especially, CNTs and graphene can be assembledinto various multi-scaled macroscopic structures, includingone dimensional fibers, two dimensional films and three di-mensional architectures, endowing the facile design of flexiblesensors for wide practical applications. In addition, the hybridstructured carbon materials derived from natural bio-mate-rials also showed a bright prospect for applications in flexiblesensors. This review provides a comprehensive presentation offlexible and wearable sensors based on the above variouscarbon materials. Following a brief introduction of flexiblesensors and carbon materials, the fundamentals of typicalflexible sensors, such as strain sensors, pressure sensors,temperature sensors and humidity sensors, are presented.Then, the latest progress of flexible sensors based on carbonmaterials, including the fabrication processes, performanceand applications, are summarized. Finally, the remainingmajor challenges of carbon-based flexible electronics are dis-cussed and the future research directions are proposed.

Sensitive biosensing strategy based on functional nanomaterials

The first decade of the 21st century has been labeled as "the sensing decade". The functional nanomaterials offer excellent platforms for fabrication of sensitive biosensing devices, including optical and electronic biosensors. A lot of works have fo- cused on the biofunctionalization of different nanomaterials, such as metal nanoparticles, semiconductor nanoparticles and carbon nanostructures, by physical adsorption, electrostatic binding, specific recognition or covalent coupling. These biofunc- tionalized nanomaterials can be used as catalysts, electronic conductors, optical emitters, carriers or tracers to obtain the ampli- fied detection signal and the stabilized recognition probes or biosensing interface. The designed signal amplification strategies have greatly promoted the development of stable, specific, selective and sensitive biosensors in different fields. This review in- troduces some novel principles and detection strategies in the area of biosensing, based on functional nanomaterials. The gen- eral methods for biofunctionalization of nanomaterials with biomolecules and their biosensing application in immunoassay of protein, DNA detection, carbohydrate analysis and cytosensing are also described.

Functional nanogenerators as vibration sensors enhanced by piezotronic effects

ZnO nanomaterials have been shown to have novel applications in optoelectronics, energy harvesting and piezotronics, due to their coupled semiconducting and piezoelectric properties. Here a functional nanogenerator （FNG） based on ZnO nanowire arrays has been fabricated, which can be employed to detect vibration in both self-powered （SP） and external-powered （EP） modes. In SP mode, the vibration responses of the FNG can be measured through converting mechanical energy directly into an electrical signal. The FNG shows consistent alternating current responses （relative error 〈 0.37%） at regular frequencies from 1 to 15 Hz. In EP mode, the current responses of FNG are significantly enhanced via the piezotronic effect. Under a forward bias of 3 V, the sensor presented a sensitivity of 3700% and an accurate measurement （relative error 〈 0.91%） of vibration frequencies in the range 0.05-15 Hz. The results show that this type of functional nanogenerator sensor can detect vibration in both SP and EP modes according to the demands of the applications.

Humidity-responsive nanocomposite of gold nanoparticles and polyacrylamide brushes grafted on Ag film: synthesis and application as plasmonic nanosensor

A general stepwise strategy for the preparation of new humidity-responsive plasmonic nanosensor was described for the first time, based on Ag film functionalization by polyacrylamide（PAAM） brushes via surface-initiated atom transfer radical polymerization（SI-ATRP） method and then assembled with gold nanoparticles（Au NPs）. We designed by this way a new plasmonic device made of Au NPs embedded in a humid vapor responsive polymer layer on Ag film and extensively characterized by surface-enhanced Raman scattering（SERS）. When the relative humidity（RH） is above 50%, the number of plasmonic hotspots decreases, causing SERS signal reduced noticeably, for the volume expansion of PAAM brushes varied the nano-gap between closely spaced Au NPs, and between Au NPs and Ag film. The reversible optical properties of the prepared nanocomposite tuned by RH were probed through SERS using 4-mercaptopyridine（4-Mpy） as a molecular probe, and the decrease of the RH reversibly induces a significant enhancement of the 4-Mpy SERS signal. By means of the high reversibility, the RH responsive nanocomposite developed in this paper provides a dynamic SERS platform and can be applied as plasmonic nanosensor which is proved to be stable for at least two months.

A novel strategy for immobilization of thionine based on calcium carbonate-gold nanoparticles inorganic hybrid composite and its application in hydrogen peroxide sensor

A novel strategy for efficient immobilization of electroactive Thionine(Th)on the gold(Au)electrode surface based on calcium carbonate-gold nanoparticles(CaCO3-AuNPs)inorganic hybrid composite was proposed and conducted by the strong electrostatic interaction between positively charged Th and negatively charged CaCO3-AuNPs composite.The hybrid composite was obtained by the adsorption of AuNPs onto the surface of CaCO3 microspheres through electrostatic interaction.Due to the microporous architecture,large surface area,and good biocompatibility of CaCO3-AuNPs composite,the amount and stability of the immobilized Th were highly strengthened.The application of the resulting Th modified electrode in the hydrogen peroxide(H2O2)sensor was also investigated.It exhibited rapid response to H2O2 within 3 s.The linear calibration ranged from 8.00×107to 1.06×10 -3mol/L with a detection limit of 2.00×10 -7mol/L.

A nano-functionalized real-time electrochemiluminescent biosensor for alanine transaminase assay

An electrochemiluminescent (ECL) biosensor was constructed for selective assay of alanine aminotransferase (ALT) based on the enzymatically catalyzed oxidation of pyruvate by pyruvate oxidase (PYOD). The composite of potassium ferricyanide and carbon nanotube was adopted to pre-functionalize the basal platinum electrode while the potassium ferricyanide acted as the activator of PYOD. The ALT catalyzed the reaction of L-alanine and-ketoglutarate to produce pyruvate which could be further enzymatically oxidized by PYOD to yield H2O2 to intensify the ECL of luminol. The biosensor showed rapid response for real-time measurement of ALT in the linear concentration range from 0.00475 to 350 U/L (r = 0.993) with a relatively standard deviation of 2.5% (CALT = 47.5 U/L,n = 6). The biosensor was applied to assay the ALT in rat serum with average recovery of 90.5%.